This is a continuation of application Ser. No. 941,993, filed Dec. 15, 1986, now abandoned.
1. Field of the Invention
This invention is in the field of processing and packaging soy protein products, such as soybean meal, soy flours and soy protein concentrates for human consumption and animal feeds.
2. Prior Art
U.S. Pat. No. 4,153,738 discloses the formation of toasted soy protein flakes, obtained from steam conditioned/flakes cracked soybeans which have been deoiled (defatted) normally with the aid of an organic solvent, i.e. hexane, by texturizing said flakes in an Anderson expeller or in a similar later model screw press model employing the combination of steam/temperature and pressure, fragmenting the texturized protein, hydrating the fragments (moisture content 12 to 25%), and rolling same into a flaked shape at a temperature that will impart sufficient toasting to the flakes.
An article by Rahman et al in the Journal of Food Processing and Preservation 2:285-298 (1979) discloses compressed freeze dried foods having a natural cellular structure with collapsed void spaces as a result of moisture removal during the drying step.
U.S. Pat. No. 3,463,641 teaches high pressure compacting of a variety of foods and food ingredients, including soy protein products into a disk for color analysis.
British patent No. 588,354 discloses compression of unspecified food products.
A number of patents are directed to texturizing soy protein by heat and pressure U.S. Pat. No. 4,057,656 (Spiel); U.S. Pat. No. 4,103,034 (Ronai); and U.S. Pat. No. 4,153,738. In addition, U.S. Pat. No. 3,843,816 (Towba) and U.S. Pat. No. 3,886,298 (Hayes) disclose texturizing protein by heating and compressing followed by expansion.
In the present invention, an approach was found to creating a fabricated spongelike material made from defatted soy protein particulates, namely defatted soy flours and soy protein concentrates which are capable of being compressed in molded cavities to form dense unitary structures having sufficient integrity to withstand easy fragmentation during shipping and commercial handling yet capable of ready rehydration. The generation of sponge-like character is accomplished through a texturizing process. This texturizing process provides cellular structure similar to natural cellular structures.
More specifically, it was discovered that soy flour (50% protein) and soy protein concentrate (65 to 72% protein) could not be simply wetted and compressed into a high density product because the steam conditioning and flaking prior to the deoiling process with solvents apparently obliterates the void spaces in their cellular structure, in contrast to naturally textured fruits and vegetables, such as those described in the prior art. These natural products, by not having been subjected to any severe physical treatment, will retain their original porous structure even after freeze drying, and are capable of being rehydrated by virtue of the existing void spaces in their cellular structure.
It was discovered that soy flours and protein concentrates had to first be texturized by extruding these products in a moistened state, accomplished by admixing water to the dry material. Only after such texturization and adjusting the water content to about 10 to 20% was it possible to compress the material, applying compression pressures of 1,500 to 3,000 lbs/sq. in. in a manner that resulted in a high density product which would greatly expand on rehydration.